In this cartridge and in other cartridges which are commercially available, the storage cylinders are of equal length. A precise proportioning of the components is obtained by a precise advance of the thrust rods and hence of the pistons, and no consideration is given to the cross-sectional area of the dispensing openings of the storage cylinders or of the dispensing channels of the cartridges. Therefore, regardless of the cross-sectional area of the storage cylinders, the dispensing openings generally have approximately the same dimensions for technical reasons associated to injection-molding. At the beginning of the dispensing operation, or after removing the closure, this leads to a greater quantity being delivered from the larger cartridge to the mixer tube, whereby a certain initial volume is rendered useless and must be discarded. In addition to the loss of material, this results in an unnecessary pollution through a substance which is generally unhardenable, and to an uncertainty as to the correct mixing ratio.